16561521 has 12 divisors (see below), whose sum is σ = 25181520. Its totient is φ = 10459800.

The previous prime is 16561513. The next prime is 16561543. The reversal of 16561521 is 12516561.

It is a happy number.

16561521 is a `hidden beast` number, since 1 + 656 + 1 + 5 + 2 + 1 = 666.

It is not a de Polignac number, because 16561521 - 2³ = 16561513 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16561511) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 48255 + ... + 48596.

It is an arithmetic number, because the mean of its divisors is an integer number (2098460).

Almost surely, 2^16561521 is an apocalyptic number.

It is an amenable number.

16561521 is a deficient number, since it is larger than the sum of its proper divisors (8619999).

16561521 is a wasteful number, since it uses less digits than its factorization.

16561521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96876 (or 96873 counting only the distinct ones).

The product of its digits is 1800, while the sum is 27.

The square root of 16561521 is about 4069.5848682636. The cubic root of 16561521 is about 254.8981831119.

The spelling of 16561521 in words is "sixteen million, five hundred sixty-one thousand, five hundred twenty-one".